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Title: Tritiated Water on Molecular Sieve without Hydrogen Production

Abstract

Several molecular sieve beds loaded with tritiated water failed to generate hydrogen gas from tritium self-radiolysis at the expected rate. Preliminary gamma-ray irradiation experiments of 4A molecular sieve with varying amounts of oxygen in the over-gas evoke a quenching mechanism. The data suggest that the gas phase rate constant for the production of hydrogen gas is several orders of magnitude smaller than the third order rate constant for scavenging of radical fragments by oxygen.

Authors:
Publication Date:
Research Org.:
Savannah River Site (US)
Sponsoring Org.:
US Department of Energy (US)
OSTI Identifier:
786596
Report Number(s):
WSRC-MS-2001-00032P
TRN: AH200132%%282
DOE Contract Number:
AC09-96SR18500
Resource Type:
Conference
Resource Relation:
Conference: 6th International Conference on Tritium, Tsukuba (JP), 11/11/2001--11/16/2001; Other Information: PBD: 10 Sep 2001
Country of Publication:
United States
Language:
English
Subject:
08 HYDROGEN; HYDROGEN; HYDROGEN PRODUCTION; IRRADIATION; MOLECULAR SIEVES; OXYGEN; PRODUCTION; QUENCHING; RADICALS; SCAVENGING; TRITIUM; TRITIUM OXIDES

Citation Formats

Walters, R.T.. Tritiated Water on Molecular Sieve without Hydrogen Production. United States: N. p., 2001. Web.
Walters, R.T.. Tritiated Water on Molecular Sieve without Hydrogen Production. United States.
Walters, R.T.. Mon . "Tritiated Water on Molecular Sieve without Hydrogen Production". United States. doi:. https://www.osti.gov/servlets/purl/786596.
@article{osti_786596,
title = {Tritiated Water on Molecular Sieve without Hydrogen Production},
author = {Walters, R.T.},
abstractNote = {Several molecular sieve beds loaded with tritiated water failed to generate hydrogen gas from tritium self-radiolysis at the expected rate. Preliminary gamma-ray irradiation experiments of 4A molecular sieve with varying amounts of oxygen in the over-gas evoke a quenching mechanism. The data suggest that the gas phase rate constant for the production of hydrogen gas is several orders of magnitude smaller than the third order rate constant for scavenging of radical fragments by oxygen.},
doi = {},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Mon Sep 10 00:00:00 EDT 2001},
month = {Mon Sep 10 00:00:00 EDT 2001}
}

Conference:
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  • The production of fusion energy in a Tokamak using deuterium and tritium requires the safe handling and processing of exhaust gases that contain various amounts of tritium. Initial operation of the Tokamak Fusion Test Reactor (TFTR), Princeton Plasma Physics Laboratory, oxidized exhaust gases for tritium recovery or long-term storage. One of the most efficient and safest ways to contain tritiated water is to sorb it onto a pelletized 4A molecular sieve. A Disposable Molecular Sieve Bed (DMSB) was designed as a pressure vessel because of the possibility of pressure generation from the radiolysis of tritiated water on molecular sieve. Hydrogenmore » production contributes to the complexity of the containers used to transport and store tritiated water, and increases the fabrication costs. Two months after removing a DMSB from the process at TFTR, a pressure in excess of that predicted from self-radiolysis was observed. Interestingly, pressure measurements at longer times (up to 2.5 years) showed less pressure than expected. Pressure was not being generated in the DMSBs at the predicted rate. This was unexpected and prompted an investigation into the mechanism responsible for the anomalous pressure measurements.« less
  • Samples of 4 A molecular sieve containing 5, 20, and 35 wt % H/sub 2/O were irradiated in sealed containers in a /sup 60/Co ..gamma..-ray source. A previous study showed that the effects of tritium ..beta..-radiolysis can be closely simulated by /sup 60/Co ..gamma..-radiolysis. During radiolysis, the pressure of the containers was monitored, and the gas composition was determined. Results indicated that H/sub 2/ was the only gas produced. O/sub 2/ in air sealed in the container was depleted by radiolysis. Final pressures depended on the amount of tritium and H/sub 2/O present. At low tritium and low water contents,more » the final pressures were low (15 psi for 7 curies tritium/g sieve and 20 wt % H/sub 2/O). The maximum initial 100-eV yield for H/sub 2/ was 0.3 molecules/100-eV. Based on these results, TA 2-880 concerning tritium waste storage can be revised to permit containers of tritiated water sorbed on molecular sieve to be accepted for safe storage.« less
  • The production of fusion energy in a tokamak using deuterium (D) and tritium (T) requires the safe handling and processing of exhaust gases that contain various amounts of tritium. Initial operation of the Tokamak Fusion Test Reactor (TFTR), Princeton Plasma Physics Laboratory, oxidized exhaust gases for tritium recovery or long-term storage. One of the most efficient and safest ways to contain tritiated water is to sorb it onto a pelletized 4A molecular sieve. For that reason, a disposable molecular sieve bed (DMSB) was designed as a pressure vessel because of the possibility of pressure generation from the self-radiolysis of tritiatedmore » water. Two months after removing a DMSB from the process at TFTR, a pressure in excess of that predicted from self-radiolysis was observed. Interestingly, pressure measurements at longer times (up to 2.5 yr) showed less pressure than expected. Pressure was not being generated in the DMSBs at the predicted rate. This was unexpected and prompted an investigation into the mechanism responsible for the anomalous pressure measurements.« less
  • A systematic program to study the long term generation of gas which results when tritiated water is stored on molecular sieve is ongoing at the Tritium Systems Test Assembly (TSTA). The gas that is generated, as the tritium decays, may result in safety concerns because the pressure generated in the disposal container may lead to a failure of the container. The study addresses both the effects of helium evolution and the effects of radiolysis. The results of the study will aid in the development of packaging requirements for the final disposal container. 1 ref., 9 figs., 1 tab.